For a relay network including a plurality of nodes (relaying devices), there have been methods such as one in which a node having a lower remaining battery level is made less selectable as a parent node, and one in which a node on a route including a node having a low remaining battery level is made less selectable as a parent node. In either method, if only those nodes having short remaining operating times are available to be selected as a parent node, there is no option but to select a node having a short remaining operating time as the parent node.